Respiratory System

1. Respiratory System

2. Non-respiratory functions of the system: 1-water loss and heat elimination, also keeps alveoli wet 2-inhances venous return 3-acid-base balance 4-enables speech 5-defends against foreign inhaled matters. 6-removes, modifies, & activate or inactivate materials “prostglandins” 7-smelling 8-shape of the chest 9-protects heart & vessels 10-aireate the blood between respiratory phases

3. Respiratory Physiology Structure : Air conducting channels Respiratory spaces  lungs float in the thoracic cavity + pleura

4. Respiratory passages comprises two portions A- Conducting part 1- Nose and mouth 2- Nasal cavity 3- Pharynx 4- Larynx 5- Trachea 6- Bronchi and Bronchioles Inside lungs B- Respiratory part 1- Alveolar ducts, Alveolar Sacs and alveoli inside lungs Larynx

5. Respiratory Physiology • Steps: 1- pulmonary ventilation: air flow between the atmosphere and the lungs. 2- diffusion of gasses between the alveoli and the blood. 3- transport. 4- regulation.

6. Atmosphere Steps of external respiration 1 Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs O2 CO2 Alveoli of lungs 2 Exchange of O2 andCO2 between air in the alveoli and the blood CO2 O2 Pulmonary circulation 3 Transport of O2 andCO2 between the lungs and the tissues Systemic circulation CO2 O2 4 Exchange of O2 andCO2 between the blood and the tissues CO2 + HO2 + HTP Internal respiration Food +O2 Tissue cell Fig. 12-1, p. 366

7. Terminal bronchiole Smooth muscle Branch of pulmonary artery Branch of pulmonary vein Respiratory bronchiole Pulmonary capillaries Alveolus Alveolar sac Pores of Kohn Fig. 12-2b, p. 367

8. Mechanics of ventilation 1.By down word and upward movement of the diaphragm  lengthen or shorten(Normal) 2.By elevation and depression of the ribs (anteropost ) ribs and sternum moves away from the spine (20% more)

9. Mechanics of ventilation Muscles : 1- Inspiratory : - Diaphragm External intercostals Sternocloidomastoid Sternum - Scalini (2 ribs) Anterior serrati

10. Mechanics of ventilation 2- Expiratory muscles : - internal intercostals Abdominal recti

11. Accessory muscles of inspiration Internal intercostal muscles Sternocleidomastoid Scalenus Muscles of active expiration Sternum Ribs External intercostal muscles Diaphragm Abdominal muscles Major muscles of inspiration Fig. 12-10, p. 373

12. Air movement • Movement of air is determined by pressures. • The lung is an elastic structure that resembles a balloon floating in the thoracic cavity . • Both lungs are surrounded by plural fluid which has negative pressure between the parietal a visceral layers

13. Lollipop “Lung” Water-filled balloon “Pleural sac” Right pleural sac Left pleural sac Parietal pleura Right lung Left lung Thoracic wall Visceral pleura Pleural cavity filled with intrapleural fluid Diaphragm Pleural cavity filled with intrapleural fluid Fig. 12-4, p. 369

14. Respiratory pressure 1- Pleural pressure: fluid pressure slight suction that helps the lungs to open at rest . (-5 to -7.5)cm H2O, during normal inspiration.

15. Respiratory pressure 2- Alveolar pressure : the pressure Inside the Alveoli: A- Glottis open, no air flow 0 cm H2O B- Inward flow sub atmospheric (-1 cm H2O) within 2s C- Outward flow positive (1 cm H2O) within 2-3s.

16. Atmospheric pressure (the pressure exerted by the weight of the gas in the atmosphere on objects on the Earth’s surface—760 mm Hg at sea level) Atmosphere 760 mm Hg Airways Thoracic wall Intra-alveolar pressure (the pressure within the alveoli—760 mm Hg when equilibrated with atmospheric pressure) Plural wall Lungs Intrapleural pressure (the pressure within the pleural sac—the pressure exerted outside the lungs within the thoracic cavity, usually less than atmospheric pressure at 756 mm Hg) 756 mm Hg Fig. 12-5, p. 370

17. Respiratory pressure 3- Transpulmonary pressure : Pressure difference between the alveolar pr. and pleural pr. [pr.differ. b/w alveoli and outer surfaces of the lungs] it measures elastic forces that tend to collapse the lungs each point of expansion [recoil pressure] .

18. Airways Pleural cavity (greatly exaggerated) Lung wall Lungs (alveoli) Thoracic wall Transmural pressure gradient across lung wall = intra-alveolar pressure minus intrapleural pressure Transmural pressure gradient across thoracic wall = atmospheric pressure minus intrapleural pressure Numbers are mm Hg pressure. Fig. 12-7, p. 371

19. Inspiration Expiration Intra-alveolar pressure Atmospheric pressure Transmural pressure gradient across the lung wall Intraplural pressure Fig. 12-13, p. 375

21. 760 Puncture wound in chest wall 760 760 760 760 756 756 Traumatic pneumothorax (Continue to the next slide) Numbers are mm Hg pressure. Fig. 12-8a, p. 371

22. 760 Hole in lung 760 760 760 760 756 756 Spontaneous pneumothorax Numbers are mm Hg pressure. Fig. 12-8c, p. 371

23. 760 760 760 760 760 760 756 Collapsed lung (Continue to the next slide) Numbers are mm Hg pressure. Fig. 12-8b, p. 371

24. Compliance of the lungs Expandability of the lungs  stretch ability of the lungs. The extent to which the lungs will expand for each unit increase in transpulmonary pr. total compliance of both lungs is around 200 ml/cm H2O transpulmonary pressure .

25. Compliance of the lungs

26. Compliance of the lungs A. the curves in the figure above depend on the elastic forces of the lungs : 1) elastic forces of the lung tissue (elastin and collagen fibres) (1/3 of the total force) 2) Surface tension of the fluid (2/3 of the total force) Surface tension is huge when surfactant is absent : H2O molecules on the surface of the water have an extra strong attraction for one another attempting to contract and collapse the alveoli.

27. Compliance of the lungs B. Surfactant : surface-active agent in water secreted by type II alveolar epithelial cells (10% of surface area of alveoli). Phospholipids, dipalmitoylphosphotidylcholine (DPPC) proteins (apoprotein), and ions (calcium) that help in spreading phospholipids

28. Compliance of the lungs

29. Compliance of the lungs Pressure generated by S.T = 2x S.T. Radius Effect of size of the alveoli on collapsing pr.: The Radius is inversely proportional to coll. pr. So smaller alveoli have greater pr. than the larger ones. premature babies have small alveolar radius and less surfactant  tendency for lung collapse is 6-8 times greater than in adults  Respiratory distress syndrome of the newborn

30. Compliance of the lungs Instability of the alveoli (rupture), Safety factors: Interdependence phenomenon (Sharing septal walls) 2. 50 000 functional units w/ fibrous septa 3. Surfactant effect : a) reduces S.T from 8 to 3 cm H2O b) [surfactant] in smaller alveoli > than in large

31. Compliance of the lungs -Compliance of thorax and lungs : 110 ml/cm H2O pr. - At high volume or compressed to low volumes, the compliance can be as little as one-fifth that of lungs alone .

32. Work of breathing -Work of breathing: 1.work required to expand the lungs against the lung and chest elastic forces (compliance work) 2.work required to overcome the viscosity of the lung and chest wall (tissue resistance work) 3. work required to overcome airway resistance (airway resistance work)

34. Minute respiratory volume :  Total volume of new air moved into respiratory passages each minute MRV=TV * freq. Normal = 500 x 12 = 6L/min (1.5 L/min fatal). ( high value like 200 L/min is fatal).

35. Alveolar ventilation : rate at which new air reaches these areas (respir. spaces) . (TV – D.S)* freq. = 4.2L/min

36. Table 12-2, p. 383

37. Respiratory passageway: • 1-Main resistance to the airflow present in • Large bronchioles and bronchi • 2-Sympathetic system dilate bronchioles • 3-Parasympatheic system constrict bronchioles • 4-Irritation of membrane passageways cause constriction as(smoking, dust, Infection)

38. 5- Histamine and slow reactive substance of anaphylaxis secrete locally by the lungs • By mast cells during allergic reaction as in • Asthma. These cause bronchiolar constriction • 6-Atropine relax respiratory passageway.